Process for the production of composite fibers, apparatus suitable to realize the same and fibers obtained thereby

ABSTRACT

A synthetic composite fiber is produced by a novel process and apparatus which includes drawing the yarn by air-suction and subjecting the yarn to a high temperature thermal shock to obtain a rigid wave or crimp in the fiber and thereafter applying a continuously high but decreasing temperature to obtain uniform crystallization of the fiber.

United States Patent [191 Conti et al.

[ Dec. 18, 1973 1 PROCESS FOR THE PRODUCTION OF COMPOSITE FIBERS, APPARATUS SUITABLE TO REALIZE THE SAME AND FIBERS OBTAINED THEREBY [75] Inventors: Walter Conti; Pasquale Corsini,

both of San Donato Milanese, Italy [73] Assignee: Snam Progetti S.p.A., San Donato,

Milanese, Italy [22] Filed: June 10, 1971 [21] App]. N0.: 151,860

[30] Foreign Application Priority Data June 10, 1970 Italy ..25751A/70 [52] US. Cl. 28/72.3, 28/72.3, 57/157 5 [51] Int. Cl. D02] 1/22, DO2g 1/18 [58] Field of Search 28/1.4, 71.3, 72.12,

28/72.17; 57/34 B, 55.5, 157 F, 157 S; 264/210, 290, 168

[56] References Cited UNITED STATES PATENTS 3,069,836 12/1962 Dahlstrom et a1. 28/72.12 X

3,448,501 6/1969 Buzano 28/72.12 3,551,549 12/1970 Sundbeck 28/7L3 X 3,558,760 1/1971 Olson 28/72.12 X 3 ,655,862 4/1972 Dorschner et a1. 28/72.17 X

Primary E.raminerWerner H. Schroeder Attorney-Ralph M. Watson 5 7 ABSTRACT A synthetic composite fiber is produced by a novel process and apparatus which includes drawing the yarn by air-suction and subjecting the yarn to a high temperature thermal shock to obtain a rigid wave or crimp in the fiber and thereafter applying a continuously high but decreasing temperature to obtain uniform crystallization of the fiber.

3 Claims, 2 Drawing Figures PATENTED DEC 18 I975 HEET 1 [IF 2 v INVENTORS ATTORNEY BY 'WW.W

PMENTEU DEC 18 I975 (mg/den) SHEET 2 BF 2 PROCESS FOR THE PRODUCTION OF COMPOSITE FIBERS, APPARATUS SUITABLE TO REALIZE THE SAME AND FIBERS OBTAINED THEREBY The present invention relates to a process for the production of composite fibers, to the apparatus suitable to realize the same and to the fiber article itself.

More particularly the present invention relates to a process for the production of composite fibers constituted by two polymers and/or copolymers, having different physical and/or chemical characteristics by means of which process said fibers acquire a helocoidal tridimensional configuration which gives the final manufactured fiber bulk and comfort; further the invention relates to the apparatus suitable to realize the process and to the fibers produced by the apparatus and process of the invention.

The suitable polymers may be different also exclusively in the molecular weight or in the crystallization velocity, the main difference consisting however in the different shortening of the two polymers constituting each filament when this is drawn and treated at suitable temperatures, higher than the ones the manufactured fiber is thereafter subjected to, namely the ones of dyeing, washing and the like.

The composite fibers leaving the spinneret plate are drawn and after drawing they have a potential for more than an actual crimping potential so that for developing all the crimping the yarns have to be subjected to a heat treatment commonly called (development). In the art, for obtaining composite fibers, processes are known by which the (development) heat treatment produces a certain bulking effect. By the known art techniques there are however many drawbacks; in fact in some of said processes the exclusive use of feeding calenders or rolls facilitates the entanglement of the yarns on the rolls and therefore frequent breakage.

In other known processes the development is carried out under tension which is often feeble or weak, resulting in reduced and irregular crimping whereby the manufactured fibers present scarce bulk and above all are unsightly in appearance and contain dyeing flaws. It is to be added also that the bicomposed filament obtained by the known techniques contains an insufficiently rigid crimping so that, after knitting or weaving operations, because of the relative tensions present in such manufacturing operations due to the frictions among crossing of the threads, the bulk of the fiber in the finished cloth is even further lowered.

We have found, and this is an object of the present invention, a process for the production of synthetic composite fibers consisting of the following steps:

a drawing the yarn taken from a bobbin so as to give the yarn low crystallinity and high molecular orientation so that the yarn is characterized by an elongation at break lower than 16 percent, preferably of 8 percent;

b. letting the stretched yarn pass through a system of devices which facilitate the separation of the individual filaments of the yarn either by tribe-electric effect or by a suitable applied electric potential or by corona discharge;

0. (developing) the yarn by means of an air-suction sucking the same by device having the task of separating more completely the filaments, also possibly by electric effect, allowing high production rates without entangling filaments on rolls because of no contact with mechanical devices, and thereafter subjecting the sucked yarn to a thermal shock and keeping the same at a high decreasing temperature for a time sufficient for the crimping development; and

d. collecting the so treated yarn on a suitable picker or bobbin.

The thermal shock is a necessary feature for obtaining a sufficiently rigid wave or crimp. It is obvious that the tridimensional waviness must have reversals of the rotation direction, medium yarn twisting being zero; we have found that the higher the number of reversals of the rotation direction the higher the crimping stiffness. We have also found that the higher the thermal shock, the more frequent are reversals. Further, we have found that subsequent high temperature treatment allows the crystallinity to be made uniform, thereby avoiding dyeing flaws. By means of the aforesaid process a yarn is obtained having textile characteristics remarkably better than those of yarns obtained by the known art processes.

A further object of the present invention is the provision of apparatus by means of which the process object of the present invention may be carried out, which is illustrated in the accompanying drawing, FIG. 1. The apparatus is comprised of bobbin 1 for collecting the yarn coming from the spinneret (not shown), a feeding calender 2, a stationary pin 3 heated at a temperature in the range of from 60C to 100C, preferably of about C, a stationary idle roll 4, a drawing godet 5, an electrically-charged ring 5a through which the yarn passes for separating the individual filaments of the yarn from one another, a pistol 6 working with air (Venturi) substantially in the form of an ejector (said pistol sucks the yarn through the system, thereby eliminating the drawbacks of entanglements present in conventional systems which make use of rolls, and further allows high (development) rates), an oven or other suitable heating device 7 wherein after a zone at a temperature ranging from 200C to 600C, preferably from 250C to 350C, (in said zone the thermal shock occurs, which shock makes frequent the wave reversals necessary for increasing crimping stiffness) a zone is present sufficiently long, at a high decreasing temperature wherein the highest yarn crystallization occurs (said crystallization is necessary for eliminating dyeing flaws) and at last, a discharging calender 8 which feeds the collecting device 9 for collecting the finished yarn on the picker or bobbin 10.

By thermal shock is meant the sudden temperature rise to which the yarn is subjected at the oven entrance,

since the yarn at the oven entrance is substantially lower than the temperature of the first zone of the oven. In a preferred embodiment of the invention the yarn and the air at the entrance to the oven are at room temperature. The oven temperature after said first zone lowers naturally because of the natural emission of air at room temperature into the oven.

A further object of the present invention is a filament constituted by two polymers having a ratio by weight preferably of l/ l a number of waves per centimeter in the range of from 6 to 12, preferably of about 10, a rate of from 5 to 25 percent, preferably of about 10 percent, wherein the rate is defined by the following formula:

rate (length under 100 mg/dn length under 1 mg/dn)/(length under 100 mg/dn) dn denier a number of reversals of the waves being higher or equal to the number of the waves, the reversals being distributed with a logarithmical-probabilistic law of standard deviation lesser than 1.0, a bulk higher than 3.0 (T. Belleli J. F. Gujemmet Bulletin de llnstitute Textile de France 1 I7, 183, 1965) and without closed points, wherein for closed points we mean the ones in stretching a yarn comprised of a plurality of said fibers;

applying an electric charge to the stretched yarn,

thereby separating the individual filaments of the yarn from one another;

applying air suction to said yarn to further separate said individual filaments from one another and to pass said yarn to a heating zone;

applying a high temperature thermal shock to said yarn to thereby develop a rigid crimp or wave in said fibers of said yarn; and'thereafter applying a continuously high but decreasing temperature to said yarn to thereby uniformly crystallize said fibers thereof.

2. The process as claimed in claim 1, wherein the temperature of said. thermal shock is in the range of from 200C to 600C.

3. The process as claimed in claim 2, wherein the temperature of said thermal shock is in the range of from 250C to 350C. 

1. A process for the production of composite synthetic fibers, including the steps of: stretching a yarn comprised of a plurality of said fibers; applying an electric charge to the stretched yarn, thereby separating the individual filaments of the yarn from one another; applying air suction to said yarn to further separate said individual filaments from one another and to pass said yarn to a heating zone; applying a high temperature thermal shock to said yarn to thereby develop a rigid crimp or wave in said fibers of said yarn; and thereafter applying a continuously high but decreasing temperature to said yarn to thereby uniformly crystallize said fibers thereof.
 2. The process as claimed in claim 1, wherein the temperature of said thermal shock is in the range of from 200*C to 600*C.
 3. The process as claimed in claim 2, wherein the temperature of said thermal shock is in the range of from 250*C to 350*C. 